System for controlling hydraulic circuits



Sept. 7, 1965 KARL-HEINZ BOROWSKI 3,204,409

SYSTEM FOR CONTROLLING HYDRAULIC CIRCUITS Filed Feb. 3, 1964 INVENTOR Karl -Heinz Borowski ATTORNEY United States Patent 3,204,409 SYSTEM FOR CONTROLLING HYDRAULIC CIRCUITS Karl-Heinz Borowski, Bochum, Germany, assignor to Gebr. Eickoif, Maschinenfahrik und Eisengiesserei m.b.H., Bochum, Germany, a corporation of Germany Filed Feb. 3, 1964, Ser. No. 341,926 Claims priority, application (iermany, July 25, 1963,

6 Claims. (or. 60-52) mining cutting machines, the winch of which is provided with a closed hydraulic operating loop controlled by a slide valve and including a fluid pump which drives a fluid motor. Spring-biased switching means are provided in accordance with the teachings of the aforesaid German patent, which switching means are exposed to the pressure of a hydraulic pilotor control loop fed by a servo pump. In such a system the switching means cause the slide valve to assume a position for blocking the fluid motor and for bringing the fluid pump into a neutral position where the output pressure of the pump is substantially zero in response to an overpressure in the operating loop or an underpressure or loss of pressure in the control loop. The switching meanshold the slide valve in said position upon a decrease or failure in the control pressure, and release the slide valve for manual adjustment when the pressure in the operating loop rises to normal.

In the practical use of the winch so controlled, it was found that, in response to operation of the switching means, the slide'valve passes through a critical position in which both sides of the operating loop are short-circuited prior to blocking of the fluid motor. Under the force of a load on the hauling chain for the winch, which may be loaded with more than ten tons (metric), the fluid motor, in said critical position of the slide valve, is forced to rapidly reverse its direction of rotation and to rotate at high speed. Hence, the motor is then operating as a pump, driven by the hauling chain of the winch, and feeds liquid through the not yet completely closed slide valve into that portion of the operating loop which is already 'short-circuited. The other side of the operating loop may also draw, through the not yet completely closed slide valve, liquid from that same portion of the operating loop. This mode of operation takes place for one fraction of a second only and is interrupted by the slide valve which abruptly blocks the fluid motor running at high speed.

As an overall object, the present invention seeks to eliminate the foregoing disadvantages of prior art systems of this type. In accordance with the invention, in one embodiment thereof, there is provided a winch or the like for mining machines equipped with a control loop fed by a servo pump and with a fluid pump and a fluid motor, the pump and motor being arranged to establish a closed and uninterrupted operating loop. By uninterrupted, it is meant that there are no valves in the conduits connecting the pump and motor. The invention is characterized in that, in response to an overpressure condition in the operating loop or to a reduction or failure of pressure in the control loop, the pressure responsive switching devices are effective to bring the fluid pump, which feeds the operating loop, into a neutral position. In this neu- 3,204,409 Patented Sept. 7, 1965 "ice tral position, the fluid motor is blocked; the pump is held in said neutral position when the pressure in the control loop is below the minimum permissible control pressure; and the pump is released for re-starting when the pressure in the operating loop drops to the normal operating pressure. Thus, in accordance with the invention, a slide valve for separating the fluid pump from the fluid motor is omitted. Instead of such slide valve, it is the fluid pump which is controlled by pressure responsive switching devices such that the pump takes over the function of the slide valve, the switching devices being responsive to the pressure in the operating loop or to the control pressure of the control loop. Hence, the fluid pump and the fluid motor may be interconnected through an uninterrupted operating loop. In this manner a considerably smoother operating characteristic of the winch is obtained, since all sudden load changes in the operating loop caused by switching operations are eliminated by arranging the switching members externally with respect to the operating loop.

In the past, fluid pumps have been connected to fluid motors by means of an uninterrupted operating loop wherein the switching members are arranged externally relative to the operating loop. Such an arrangement, for example, is shown in Olhydraulik und Pneumatik, vol. 1, Grundschaltplane hydraulischer Anlagen, page 33 (German publication). However, in contrast to such prior art systems, the switching devices 'of the present invention which are responsive to pressure variations in the operating loop or control loop, and which are operative to determine the position or adjustment of the fluid pump, are characterized by the provision of a distributing and flushing valve which, under the elfect of the pressure side of the operating loop, is forced in one direction or the other against the force of a spring. As will be seen, the distribution-flushing valve is effective in this manner to direct the pressure of the operating loop against a springbiased turn-oft and safety valve and, simultaneously, to connect the low pressure side of the operating loop with a flushing pressure valve, such as that shown in German Patent No. 1,060,819. In this manner, the turn-01f safety valve, in response to an overpressure condition in the operating loop, is responsive only to the pressure of the operating loop against the spring force and is, hence, effective to disconnect the control circuit from the turn-on device of the fluid pump and to connect the turn-on device with a sump or reservoir. At the same time, the turn-off safety valve is effective to connect the high pressure side of the operating loop with the low pressure side thereof in response to a larger displacement of the turnolf safety valve. That is, the high and low pressure sides of the operating loop will be interconnected when the overpressure continues for relatively long periods of time with the control loop releasing the turn-on device of the fluid pump.

In a further refinement of the invention, there may be provided a power control apparatus which is operated from the high pressure side of the operating loop through a distribution-flushing valve to thereby control the delivery quantity adjustment of the fluid pump such that the winch or other instrumentality may be operated with constant power depending upon the pressure of the operating loop.

A particularly suitable construction of the apparatus for carrying out the system of the invention is accomplished when the power control member, which eflects adjustment of the fluid pump independency upon the pressure of the operating loop, is associated with a reciprocable piston under the control of the pressure withing the control loop. The operating piston, depending upon its direction of movement, is effective either to bring the fluid pump into a neutral position where its output pressure is substantially zero or to release it for manual control. By telescoping into each other the piston of the power control apparatus and the aforesaid operating piston and by biasing the piston by means of a spring disposed therebetween, a particularly advantageous arrangement of these two pistons is accomplished,

as will be seen.

In critical situations, the fluid pump may be turned .oif rapidly, either manually or by remote control, withvout having to turn off the electric motor driving the fluid pump.

description taken in connection with the accompanying single figure drawing which schematically illustrates the invention.

Referring now to the drawing, there is shown a fluid .pump 1 and a servo pump 2 operatively connected with ,a drive motor, not shown, of an extraction mining machine, for example. The pump 1 drives, through conduits 4 and 4', a fluid motor 3 which drives the sprocket wheel of a winch or the like through a reduction gear, not shown. It will be noted that the conduits 4 and 4 provide an uninterrupted operating loop which includes both the pump 1 and the motor 3. The pump 1 is of the axial-piston type and includes a control lever 1B controlled by apparatus, generally indicated at 1C, to vary the output pressure of the pump as well as the direction of flow through the pump. When the lever 1B is rotated, for example, in a clockwise direction as viewed in the drawing, the conduit 4 will be pressurized to rotate the motor 3 in one direction with conduit 4' being conlever 1B in one direction or the other, the magnitude of the output pressure increasing as the lever 1B is rotated further in either direction.

The operating loop for the pump-motor combination 1, 3 includes the conduits 4 and 4' as well as conduit 66,

all of relatively large diameter. The remaining conduits, on the other hand, comprise the control loop or hydraulic control circuit for regulating the pump 1.

In operation, the drive motor, not shown, drives both the axial piston pump 1 as well as a servo pump 2 which supplies fluid under pressure to the control loop. This latter pump 2 draws oil from a sump 6 through a filter and is equipped with back-pressure valves 7 and 7' at its suction and pressure sides respectively, whereby the direction of delivery into conduit 8 is independent of any change in the direction of rotation of the pump 2. The servo pump 2 delivers pressurized liquid via conduits 8 and 9 of the control loop to a slide valve 11 which is held in its dead-center position shown in the drawing by means of a spring 10. With the slide valve 11 in the dead-center position shown, conduits 8 and 9 are connected through a slide recess 12 and conduit 13 to the left face of an operating piston 14 incorporated into the control apparatus 1C. When pump 2 rotates and pressurizes conduits 8, 9 and 13, the piston 14 is forced to the left as viewed in the drawing and into a dead-center position where its conical end section 16 fits into a matching conical groove 15 formed in the upper portion of a control sleeve 17, which sleeve 17 forms part of the control apparatus 1C. Fluid under pressure in conduit 13 is also admitted via conduit 19, check valve 39 and conduit 20 to an anticipatory control slide valve 21, the function of which will hereinafter be described in detail.

In addition to supplying fluid under pressure to conduits 8 and 9, the servo pump 2 also pressurizes conduits 24 and 38. The fluid in conduit 24 is adapted to pass through an annular recess 25 of a turn-off safety valve 26 and the conduit 27 to the underside of piston 28 of a turn-on device 28'. It will be noted that the piston 28 is normally urged into its lowermost position by means of a coil spring 29 which surrounds a pin 30. When fluid under pressure is admitted to the underside of piston 28 through conduit 27, it is forced upwardly against the force of the spring 29, whereupon the pin 30 may also move upwardly.

Upward movement of the pin 30 is effected by means of a manually-operated lever 31 which can be rotated in the direction of arrow 31' to rotate a lever arm 32 in a clockwise direction about pivot point 33. In this process, it will be appreciated that a roller 34 at the right end of the lever arm 32 engages the left end of the slide valve 11, thereby forcing the valve to the right against the force of spring 10. It should be understood, however, that when the pressure in conduit 27 falls, the spring 29 will force piston 28 and the pin 30 downwardly as viewed in the drawing whereby the roller 34 will be moved upwardly to permit the spring 10 to force valve 11 into the position shown.

Assuming that conduit 27 is pressurized by the pump 2 and that the lever 31 is manually rotated in a counterclockwise direction to lower the roller 34, the slide valve 11 will now be in a position to block conduit 9 while connecting conduit 13 with the sump or reservoir 6. This, in effect, releases the piston 14 for movement to the right as viewed in the drawing such that its conical end section can move out of the conical recess 15 in membe 17. At the same time, movement of this slide valve 11 to the right against the force of spring 10 connects conduit 35 to conduit 37 whereby the control pressure from pump 2 is applied to the left face of piston 14 to positively move its conical section out of the conical recess 15. This action releases the control sleeve 17 for setting the delivery quantity of the fluid pump 10 in a manner herein-after described.

In order to prevent disconnection of the anticipatory slide valve 21 from the control pressure with the slide valve 11 in the position just described, there is provided a conduit 38 connected to the conduit 20. The conduit 19, it will be noted, is equipped with the check valve 39 which prevents the liquid, delivered through conduit 38 by the servo pump 2, from flowing through the conduits 19 and 13 to the sump 6.

With reference now to the control apparatus 1C for the pump 1, it includes, in addition to the control sleeve 17, a regulating rod 44 which extends through a central axial opening in the control sleeve 17. As shown, the

rod 44 is biased into the central or null position shown by means of a coil spring 48. On the lower end of the rod 44 is a sleeve 46 engaged by a projection on a nut 47 threadedly received on a spindle 43. The spindle 43 may be rotated in one direction or the other by means of spur gears 41 .and 42, the gear 41 being connected as shown to a manually rotatable dial 40. Since the spring 48 will not flex under the force applied to rod 44 by the nut 47 and spindle 43, movement of the rod causes the control sleeve 17 to move simultaneously therewith. Of course, movement of the control sleeve 17 in this manner can occur only when the conical end sections 16 and 69 of piston devices 14 and 67 are retracted out of the conical recess 15.

When the control sleeve 17 moves up or down under the force of the spindle and nut arrangement 43, 47 it also moves the arm of a steering lever 50 in the respective up or down direction, the arm 50 being mounted on the rod 44 for the pivotal movement about point 49. The steering lever 50, supported in a fork 51 of the anticipatory control slide valve 21, is operatively connected to a followup piston 53 such that it may rotate about the pivot point 52. The follow-up piston comprise-s a servo power drive for the regulating lever 1B of pump 1. With the anticipatory slide valve 21 in the position shown, movement of the piston 53 upwardly or downwardly is blocked by fluid above and below it as well as in passageways 57 and 58. If, however, the rod 44 moves upwardly, the anticipatory slide valve 21 will also move upwardly, thereby connecting conduit 20 in the control loop to passageway 57 to force piston 53 and the control level 1B downwardly. In a similar manner, downward movement of rod 44 will cause downward movement of the anticipatory slide valve 21 to connect the conduit 20 to passageway 58, thereby moving both the piston 53 and control lever 1B upwardly. In this process, the passageway 57 or 58 which is not connected to conduit 20 is connected through either recess 55 or 56 to the sump 6 to complete the hydraulic circuit.

Hence, the follow-up piston 53 moves in a direction opposite to the direction of movement of the anticipatory control slide valve 21 until the latter is pushed back into the illustrated center position by the follow-up piston 53 and the steering lever SO which pivots about the pivot point 49 of the regulating rod 44. The fluidpump 1 is now adjusted for the desired setting as to delivery, direction and quantity; and the follow-up piston 53 is blocked again in its position by means of the anticipatory control slide valve 21.

In order to increase the accuracy of setting the delivery quantity and to eliminate the lost motion betweenthe rod 44, the anticipatory slide valve 21, and the follow-up piston 53, this lost motion being caused by the pivotal mounting in the fork 51 and the pivots 49 and 52, the

anticipatory control slide valve 21 is biased by means of a spring 59 located at the face remote from the fork 51. In this manner the lost motion of the three pivoted devices is rendered ineffective.

Under the conditions just described, the pump 1 is in its operating position and, depending upon the setting of the direction of rotation, delivers fluid either into the conduit 4 or the conduit 4' of the closed operating loop, thereby driving the fluid motor 3 in the corresponding direction of rotation at a speed corresponding to the delivered quantity. Depending upon the direction of rotation of the pump, either the upper face of adistribution-flushing valve 63 or the lower face thereof is subjected to the pressure of the operating loop and the valve 63 pushed against the force of a spring 64 in one direction or the other. For example, if the conduit 4 is the high pressure side of the operating loop, fluid under pressure will flow through conduit 60, recess 61 and bore 62. This moves the valve 63 downwardly as viewed in the drawing. Similarly, if the conduit 4' comprises the high pressure side of the conduit 60', recess 61 and bore 62 are subjected to the pressure of the operating loop and the valve 63 pushed upwardly against the force of spring 64.

When the valve '63 moves upwardly or downwardly in the manner described above, the conduit 60 or 60' is connected to conduit 66 which leads to the control apparatus 1C. Specifically, the conduit 66 serves to move a piston 68 which, in turn, engages piston 67 to move its conical end section 69 toward the control sleeve 17. The piston 67 ordinarily will not move the control sleeve 17 and the lever 50 into the dead-center or null position, but acts to cause a reduction in the delivery quantity of the fluid pump 1 when the pressure in the operating loop exceeds the desired level. That is, the piston 67 acts more or less as a governor to regulate the delivery quantity of the pump 1; however it does not act to completely shut down the pump.

It will be noted that the operating piston 14 which is under the control of the slide valve 11, is arranged in a telescope-like fashion with the piston 67 under the control of the fluid pressure of the operating loop, the two pistons being biased apart by means of the spring 18. This, of course, provides a very simple and compact construction for effecting the desired result.

A set cylinder 70, disposed at the side of the control apparatus 10 opposite the pistons 14 and 67, engages the opposite side of the conical recess 15 and may, for example, be controlled by the armature current of the drive motor for pumps 1 and 2. The piston 71 within cylinder 70 is supplied with fluid pressure from a separate control circuit and is responsive to an overload or underload condition of the drive motor. The cylinder 70-piston 71 arrangement, therefore, acts as a safety device for forcing the pump 1 into its null position whenever an overload or underload condition of the drive motor occurs.

When the distribution-flushing valve 63 is moved upwardly or downwardly to connect the pressure side of the operating loop to conduit 66, pressure, is also applied to the recess 73 of turn-elf safety valve 26 through conduit 72. The pressure within recess 73 is appliedthrough a radial bore 74 to a piston 76 disposed within an axial bore of the turn-off safety valve 26 and raises the valve against the force of spring 77 when the pressure in the operating loop exceeds its maximum predetermined operating pressure. The leading edge 78 of valve 26 now slides relative to the adjacent housing edge and disconnects conduit 24 from conduit 27. At the same time, the

conduit 27 is connected to the sump 6. Hence, an overpressure in the operating loop is eifective to disconnect the control circuit from the turn-on device 28. When this occurs piston 29 and pin 30 move downwardly, roller 34 moves upwardly, and slide valve 11 moves to the left into the position shown in the drawing where conduit 37 is connected to the sump 6 while conduit 13 is connected to high pressure conduits 8 and 9. Thus, under these circumstances, the right face of the piston device 14 is pressurized to move its conical end section 16 into the conical recess 15 of sleeve 17, whereby the lever 1B is driven into its central or null position with the output pressure of the pump being substantially zero.

Upon disappearance of the overpressure condition :within the operating loop 4, 4 and return of the shut-off safety valve 26 to its position shown in the drawing,

conduit 24 is again connected to conduit 27, whereupon piston 28 is raised against the force of spring 29. The pump 1 may now be turned on again by manually rotating the lever 31 in the direction of arrow 31, and the pump 1 again operates according to the delivery quantity set by the dial 40 prior to the overload.

If the pressure peaks in the operating loop are particularly high, the piston strokes of the shut-01f safety valve 26 become longer. When this happens, the leading edge 79 of valve 26 enters recess 80 and connects the high pressure side of the operating loop with the suction or low pressure side thereof via conduits 81 and 82 or 82'. The

shut-off safety valve 26 is, therefore, effective to short circuit the operating loop and permits the flow of fluid from the low pressure side to the high pressure side upon the occurrence of particularly high pressure peaks. It is, of course, understood that in this situation the control lever 1B is returned to its null position by disconnecting conduits 24 and 27 to move piston 28 downwardly in the manner described above.

It is desirable to continuously supply filtered and cooler liquid' from the control circuit to the suction or low pressure side of the operating loop. For this purpose, the conduit 24 at the output of servo pump 2 is connected to the loop portions 4 and 4' through conduits 84 and 84', the latter conduits being provided with check valves 83 and 83, respectively. At the same time, approximately an equal amount of liquid is drained otf from the low pressure or suction side of the operating loop via the conduit 60 or 60' and the recess 61 or 62' which incorporates associated tapered sections of the distributionflushing valve 63; Depending upon the position of the 7 distribution-flushing valve 63, the fluid is admitted through conduit 82 or 82, recess 80 and conduit 85 to flushing pressure valve 86 which permits controlled amounts of fluid to flow through radiator 87 to the sump 6. These latter operations occur, as will be understood, regardless of whether an overpressure or underpressure condition occurs in the operating loop. The assembly is completed by means of check valves 88 and 89 which connect the flushing pressure valve 86 and valve 76 to the sump 6.

Although the invention has been shown in connection with 'a certain specific embodiment, it-will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may bemade to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In a hydraulic control system of the type having an .uninterrupted operating loop in which a' fluid pump .drives a fluid motor, the combination of a pressure responsive switch device, means including first and second interconnected valve devices actuable in sequence by pressure in the operating loop for actuating the pressure responsive switch device when the pressure in the operating loop rises above a predetermined maximum operating pressure, means including the first of said interconnected valve devices for regulating the output of said fluid pump when said first valve device is actuated, and means operatively connecting the switch device to the fluid pump to 7 opera-tively connecting the switch device to the fluid pump to maintain the .same in a neutral position where its operating pressure is substantially zero when the switch device is actuated, fluid motor means directly responsive to the pressure of said operating loop for causing a reduction in the delivered quantity of fluid from the pump when the pressure in the operating loop exceeds a predetermined desired operating pressure, said fluid motor means being disconnected from the operating loop when the pump is not operating, anda valve device for connecting the fluid motor means to the operating loop when the pump is operating.

3. In a hydraulic control system of the type having an uninterrupted operating loop in which -a fluid pump drives a fluid motor and including a. hydraulic control circuit supplied with fluid under pressure by a servo pump, the combination of means operatively connected to said control circuit for enabling the pump until its output pressure rises above a predetermined maximum pressure, a pressure responsive switch device actuable when the pressure in the operating loop rises above a predetermined maximum operating pressure, means operatively connecting the switch device to said fluid pump to maintain the same in a neutral position where its operating pressure is substantially zero when the switch device is actuated, a hydraulic reservoir, a flushing pressure valve, means including a distribution-flushing valve operable under the force of fluid delivered by-said pump for connecting a the low pressure side of said operating loop to the reservoir through said flushing pressure valve, and check valve means connecting the low pressure side of the operating loop to said hydraulic control circuit, the check valve means being adapted to pass fluid from the control circuit into the low pressure side of the operating loop when fluid is withdrawn from the low pressure side thrlough said distribution-flushing and flushing pressure va ves.

4. In a hydraulic control system of the type having an uninterrupted operating loop in which a fluid pump drives a fluid motor and including a hydraulic control circuit supplied with fluid under'pressure by a servo pump, the combination of valve means operatively connected to said control circuit for enabling the pump to deliver fluid until its output pressure rises above a predetermined maximum operating pressure, a pressure responsive switch device actuable when the pressure in the operating loop rises above said predetermined maximum operating pressure, means operatively connecting the switch device to said fluid pump to maintain the same in a neutral position where its operating pressure is substantially zero when the switch device is actuated, and means connecting said control circuit to the switch device to maintain the same deactuated at all times except when the pressure in the control circuit falls below a predetermined value.

5. In a hydraulic control system of the type having 7 an uninterrupted operating loop in which a fluid pump drives a' fluid motor and including a hydraulic control circuit supplied with fluid under pressure by a servo pump,

having a conical forward portion adapted to fit into said conical recess to drive said reciprocable member into a null position where the operating pressure of said fluid pump is substantially zero, spring means normally urging the conical section'of one of said piston devices into said conical recess to maintain the reciprocable member in its null position while maintaining the conical section of the other of said piston devices out of said conical recess, means connecting said hydraulic control circuit to said one piston whereby the conical portion of said one piston will be moved out of said conical recess when the pressure within the control circuit is above a predetermined minimum value, and means connecting said other piston device said conical recess to maintain the reciprocable member in its null position.

' References Cited by the Examiner UNITED STATES PATENTS 2,472,547 6/49 Purcell 6052 X JULIUS E. WEST, Primary Examiner. EDGAR W. GEOGHEGAN, Examiner. 

1. IN A HYDRAULIC CONTROL SYSTEM OF THE TYPE HAVING AN UNINTERRUPTED OPERATING LOOP IN WHICH A FLUID PUMP DRIVES A FLUID MOTOR, THE COMBINATION OF A PRESSURE RESPONSIVE SWITCH DEVICE, MENS INCLUDING FIRST AND SECOND INTERCONNECTED VALVE DEVICES ACTUABLE IN SEQUENCE BY PRESSURE IN THE OPERATING LOOP FOR ACTUATING THE PRESSURE RESPONSIVE SWITCH DEVICE WHEN THE PRESSURE IN THE OPERATING LOOP RISES ABOVE A PREDETERMINED MAXIMUM OPERATING PRESSURE, MEANS INCLUDING THE FIRST OF SID INTERCONNECTED VALVE DEVICES FOR REGULATING THE OUTPUT OF SAID FLUID PUMP WHEN SID FIRST VALVE DEVICE IS ACTUATED, AND MEANS OPERATIVELY CONNECTING THE SWITCH DEVICE TO THE FLUID PUMP TO MAINTAIN THE SAME IN A NEUTRAL POSITION WHERE ITS OUTPUT PRESSURE IS SUBSTANTIALLY ZERO WHEN THE SWITCH DEVICE IS ACTUATED. 